In electronic devices such as personal computers and game consoles, various switching converters are used. Among popular switching converters are DC/DC converters (switching regulators) and AC/DC converters. DC/DC converters are designed to step down a direct current (DC) voltage supplied from a battery or inverter to an optimal voltage level for load. AC/DC converters are designed to convert an alternating current (AC) voltage into a corresponding DC voltage.
FIG. 1 is a circuit diagram illustrating a configuration example of a switching converter 2r studied by the present inventors. The switching converter 2r illustrated in FIG. 1 is a step-down DC/DC converter and primarily includes an output circuit 10 and a control circuit (controller) 20.
The switching converter 2r steps down an input voltage VIN of an input line 4 to a given level, supplying an output voltage VOUT to a load (not shown) connected to an output line 8.
The output circuit 10 includes an input capacitor C1, an output capacitor C2, a high-side transistor (switching transistor) M1, a low-side transistor (synchronous rectification transistor) M2, and an inductor L1.
The input capacitor C1 is provided between the input line 4 and a ground line 6 to stabilize the input voltage VIN. The output capacitor C2 is connected between the output line 8 and the ground line 6 to smooth the output voltage VOUT.
The high-side transistor M1 and the low-side transistor M2 are connected in series between the input line 4 and the ground line 6, i.e., in parallel with the input capacitor C1. The inductor L1 is provided between a switching node (or also referred to as a switching line) 9 and the output line 8. The switching node is a connection point between the high-side transistor M1 and the low-side transistor M2.
The controller 20 is supplied with a feedback voltage VFB that is proportional to the output voltage VOUT. The controller 20 generates a pulse signal whose duty ratio is adjusted so that the feedback voltage VFB approaches a given reference voltage VREF. The controller 20 generates a gate voltage HG for the high-side transistor M1 and a gate voltage LG for the low-side transistor M2 in accordance with the pulse signal, complementarily switching between the high-side transistor M1 and the low-side transistor M2 with a dead time provided between the switching events. Switching between the high-side transistor M1 and the low-side transistor M2 is controlled by the controller 20, stabilizing the output voltage VOUT to a target level.